Reducing Ammonia Volatilization from Maize Fields with Separation of Nitrogen Fertilizer and Water in an Alternating Furrow Irrigation System

The objective of this 2-yr field trial, with a central composite rotatable design, was to assess and quantify the effects of separation of nitrogen fertilizer and water with alternating furrow irrigation （SNWAFI） practices on soil ammonia （NH3） emission during the summer maize （Zea mays L.） growing season. Ammonia volatilization after N sidedress and irrigation ranged from 4.8 to 17.0 kg N ha-1 and 6.2 to 20.6 kg N hal, respectively, in 2008 and 2009. The lower N input contributed to lower NH3 loss but lower yield, whereas the higher N input induced higher yield as well as higher NH3 loss. Ammonia intensity （NH3 volatilization per crop yield） after N sidedress and irrigation was 1.2-3.0 kg NH3-N t-1 yield in 2008 and 1.1-3.2 kg NH3-N t1 yield in 2009. The predicted minimum NH3 intensity in 2008 was 1.6 kg NH3-N fl yield and was obtained with the combined application of 127 kg N ha^-1 and 108 mm irrigation water. In 2009, the predicted minimum NH3 intensity was 1.3 kg NH3-N t-j yield and was obtained with the combined application of 101 kg N ha-1 and 83 mm irrigation water. We conclude that SNWAFI practices with optimum rates of water and fertilizer can significantly reduce soil NH3 intensity and maintain yield. It was more beneficial for sustainable farming strategies to minimize the NH3 intensity rather than reduce absolute NH3 emissions alone.

Effects of Nitrogen Application Level on Rice Nutrient Uptake and Ammonia Volatilization

The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potassium in rice plants across all growth stages showed a trend to increase with increasing nitrogen application levels from 0 to 270 kg/hm 2,but decreased at nitrogen application levels exceeding 270 kg/hm 2.Moreover,the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants was increased by application of organic manure in combination with 150 kg/hm 2 nitrogen.The nitrogen uptake was high during the jointing to heading stages.Correlation analysis showed that rice yield was positively correlated with the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants.The highest correlation coefficient observed was between the amount of nitrogen uptake and rice yield.The rate and accumulative amounts of ammonia volatilization increased with increasing nitrogen fertilizer application level.Compared with other stages,the rate and accumulative amount of ammonia volatilization were higher after base fertilizer application.The ammonia volatilization rates in response to the nitrogen application levels of 270 kg/hm 2 and 330 kg/hm 2 were much higher than those in the other treatments.The loss of nitrogen through ammonia volatilization accounted for 23.9% of the total applied nitrogen at the nitrogen application level of 330 kg/hm 2.

Ammonia volatilization losses and ^(15)N balance from urea applied to rice on a paddy soil

Ammonia volatilization loss and ^15N balance were studied in a rice field at three different stages after urea application in Taihu Lake area with a micrometeorological technique. Factors such as climate and the NH4^＋-N concentration in the field floodwater affecting ammonia loss were also investigated. Results show that the ammonia loss by volatilization accounted for 18.6%-38.7% of urea applied at different stages, the greatest loss took place when urea was applied at the tillering stage, the smallest at the ear bearing stage, and the intermediate loss at the basal stage. The greatest loss took place within 7 d following the fertilizer application. Ammonia volatilization losses at three fertilization stages were significantly correlated with the ammonium concentration in the field floodwater after the fertilizer was applied. ^15N balance experiment indicated that the use efficiency of urea by rice plants ranged between 24.4% and 28.1%. At the early stage of rice growth, the fertilizer nitrogen use efficiency was rather low, only about 12%. The total amount of nitrogen lost from different fertilization stages in the rice field was 44.1%-54.4%, and the ammonia volatilization loss was 25.4%-33.3%. Reducing ammonia loss is an important treatment for improving N use efficiency.

Effects of Nitrogen Application Levels on Ammonia Volatilization and Nitrogen Utilization during Rice Growing Season

We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4＋-N in surface water, loss of ammonia through volatilization from paddy fields, rice production, nitrogen-use efficiency, and nitrogen content in the soil profile. The concentration of NH4＋-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level, and peaked at 1-3 d after nitrogen application. Less ammonia was lost via volatilization from clay soil than from sandy soil. The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied, from the highest loss to the lowest： N application to promote tillering 〉 the first N topdressing to promote panicle initiation （applied at the last 4-leaf stage） 〉 basal fertilizer 〉 the second N topdressing to promote panicle initiation （applied at the last 2-leaf stage）. The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2, equivalent to 10.92%-21.76% of the nitrogen applied. The total loss of ammonia via volatilization from sandy soil was 11.32-102.43 kg/hm2, equivalent to 11.32%-25.61 % of the nitrogen applied. The amount of ammonia lost via volatilization and the concentration of NH4＋-N in surface water peaked simultaneously after nitrogen application; both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%. With the increase in nitrogen application level, rice production and nitrogen accumulation in plants increased, but nitrogen-use efficiency decreased. Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil. In the soil, the nitrogen content was the lowest at a depth of 40-50 cm. In any specific soil layer, the soil nitrogen content increased with increasing nitrogen application level, and the soil nitrogen content was higher in clay soil than in sandy soil. In terms of ammonia volatilization, the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season. However, for rice production, a suitable nitrogen application level is approximately 300 kg/hm2. Therefore, taking the needs for high crop yields and environmental protection into account, the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.

Volatilization behaviors of diesel oil from the soils

The volatilization of diesel oil, Shengli crude oil and 90# gasoline on glass surface of petri dishes were conducted at the ambient temperature of 25℃. Diesel oil evaporates in a power manner, where the loss of mass is approximately power with time. 90# gasoline evaporates in a logarithmic with time. Where as the volatilization of Shengli crude oil fit either the logarithmic or power equation after different time, and has similar R2. And the effects of soil type and diesel oil and water content on volatilization behavior in unsaturated soil were studied in this paper. Diesel oil and water content in the soils play a large role in volatilization from soils. Appropriate water helps the wicking action but too much water stops it. The wicking action behaves differently in four different types of soils in the same volatilization experiment of 18% diesel oil content and air-dry condition.

Biochar Effectively Reduces Ammonia Volatilization From Nitrogen-Applied Soils in Tea and Bamboo Plantations

Intensive practices in forest soils result in dramatic nitrogen(N)losses,particularly ammonia(NH_(3))volatilization,to adjacent environmental areas.A soil column experiment was conducted to evaluate the effect of bamboo biochar on NH_(3) volatilization from tea garden and bamboo forest soils.The results showed that biochar amendment effectively reduced NH_(3) volatilization from tea garden and bamboo forest soil by 79.2%and 75.5%,respectively.The soil pH values increased by 0.53-0.61 units after biochar application.The NH_(4)^(+)-N and total N of both soils were 13.8-29.7%and 34.0-41.9%higher under the biochar treatments than under the control treatment,respectively.In addition,the soil water contents of the two biochar-amended soils were significantly higher(P<0.05),by 10.7-12.5%,than that of the soils without biochar amendment.Therefore,biochar mitigates NH_(3) volatilization from the tested forest soils,which was due to the increases in soil NH_(4)^(+)-N,total N and water contents after biochar amendment.Our main findings suggest that biochar addition is an effective management option for sustainable forest management.

Volatilization Kinetics of Sb2S3 in Steam Atmosphere

The volatilization kinetics of antimony trisulfide in steam atmosphere was studied with thermogravimetry at temperatures from 923 to 1123 K. A theoretical model was developed to calculate the overall rate constant and the mass transfer coefficient in gas phases. The experimental results show that the volatilization rate is enhanced with increasing temperature and steam flow rate. The volatilization rate is mainly controlled by the mass transport in gas phases. The apparent activation energy for the process is found to be 59.93 kJ/mol. It is demonstrated that Sb2S3 is dominantly oxidized into Sb2O3 and H2S by water vapor in the volatilization process. Some antimony metal is formed. The reaction mechanism is discussed in accordance with experimental data.

NH3 Volatilization from Aboveground Plants of Winter Wheat During Late Growing Stages

Ammonia volatilized from aboveground parts of winter wheat was collected with an enclosure growth chamber and measured from jointing to maturing stage. The results showed that ammonia released from unfertilized plants grown in high and low fertility soils remained at low rates of 2.3 and 0. 9μg NH3 40 plant-1 h-1 respectively at late filling stage. However, fertilized plants rapidly increased the rates to 43. 4 and 52. 2μg NH3, 40 plant-1 h-1 in the high and low fertility soils, respectively, at the same period. The released a-mount was different in different parts of plants. At filling stage, lower senescing stems and leaves volatilized more ammonia than upper parts, i. e. , ears and flag leaves that grew normally, with an average of 1. 4 and 0.7μg NH3 20 plant-1 h-1 respectively, strongly suggesting that it was the senile organs that released large amounts of ammonia. At the grain filling stage, shortage of water supply (drought stress) reduced ammonia volatilization. The average rate of ammonia released under water stress was 0. 9μg NH3 40 plant-1 h-1, but 1.2μg NH3 40 plant-1 h-1 with moderate water supply. Application of N together with P fertilizer resulted in a higher ammonia volatilization than N fertilization alone at the maturing stage. The average rate released was 135.3 μg NH3 40 plant-1 h-1 when 0.4 g N and 0.13 g P had been added to per kg soil, while 33. 7μg when 0. 4 g N added alone. Ammonia volatilization from plants was closely related with plant biomass and N uptake;P fertilization increased plant biomass and N uptake and therefore increased its release.

Nitrogen mobility,ammonia volatilization,and estimated leaching loss from long-term manure incorporation in red soil

Nitrogen（N） loss from fertilization in agricultural fields has an unavoidable negative impact on the environment and a better understanding of the major pathways can assist in developing the best management practices. The aim of this study was to evaluate the fate of N fertilizers applied to acidic red soil（Ferralic Cambisol） after 19 years of mineral（synthetic） and manure fertilizer treatments under a cropping system with wheat-maize rotations. Five field treatments were examined： control（CK）, chemical nitrogen and potash fertilizer（NK）, chemical nitrogen and phosphorus fertilizer（NP）, chemical nitrogen, phosphorus and potash fertilizer（NPK） and the NPK with manure（NPKM, 70% N from manure）. Based on the soil total N storage change in 0–100 cm depth, ammonia（NH_3） volatilization, nitrous oxide（N_2O） emission, N plant uptake, and the potential N leaching loss were estimated using a mass balance approach. In contrast to the NPKM, all mineral fertilizer treatments（NK, NP and NPK） showed increased nitrate（NO_3~–） concentration with increasing soil depth, indicating higher leaching potential. However, total NH_3 volatilization loss was much higher in the NPKM（19.7%） than other mineral fertilizer treatments（≤4.2%）. The N_2O emissions were generally low（0.2–0.9%, the highest from the NPKM）. Total gaseous loss accounted for 1.7, 3.3, 5.1, and 21.9% for NK, NP, NPK, and NPKM treatments, respectively. Estimated N leaching loss from the NPKM was only about 5% of the losses from mineral fertilizer treatments. All data demonstrated that manure incorporation improved soil productivity, increased yield, and reduced potential leaching, but with significantly higher NH_3 volatilization, which could be reduced by improving the application method. This study confirms that manure incorporationis an essential strategy in N fertilization management in upland red soil cropping system.

Rice yield, nitrogen utilization and ammonia volatilization as influenced by modified rice cultivation at varying nitrogen rates

Field experiments were conducted in 2006 to investigate the impacts of modified rice cultivation systems on: grain yield, N uptake, ammonia volatilization from rice soil and N use efficiency (ANUE, agronomic N use efficiency;and PFP, partial factor productivity of applied N). The trials compared rice production using modified methods of irrigation, planting, weeding and nutrient management (the system of rice intensification, SRI) with traditional flooding (TF). The effects of different N application rates (0, 80, 160, 240 kg ha-1) and of N rates interacting with cultivation methods were also evaluated. Grain yields ranged from 5.6 to 6.9 t ha-1 with SRI, and from 4.0 to 6.1 t ha-1 under TF management. On average, grain yields under SRI were 24% higher than that with TF. Ammonia volatilization was increased significantly under SRI compared with TF and the average total amount of ammonia volatilization loss during the rice growth stage under SRI was 22% higher than TF. With increases in application rate, N uptake by rice increased, and the ratio of N in the seed to total N in the plant decreased. Furthermore, results showed that higher ANUE was achieved at a relatively low N fertilizer rate (80 kg ha-1 N) with SRI. Results of these studies suggest that SRI increased rice yield and N uptake and improved ammonia volatilization loss from rice soil compared with TF. Moreover, there were significant interactions between N application rates and cultivation methods. We conclude that it was the most important to adjust the amount of N application under SRI, such as reducing the amount of N application. Research on effects of N fertilizer on rice yield and environmental pollution under SRI may be worth further studying.

Evidence of GeO volatilization and its effect on the characteristics of HfO_2 grown on a Ge substrate

HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen,the thickness of Ge oxide＇s interfacial layer decreases,and the presence of GeO is observed at the H2 O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2 O molecules in H2 O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2 /Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy（XPS） and electrical measurements.

Inoculation with chlamydospores of Trichoderma asperellum SM-12F1 accelerated arsenic volatilization and influenced arsenic availability in soils

Fungi capable of arsenic（As） accumulation and volatilization are hoped to tackle As-contaminated environment in the future. However, little data is available regarding their performances in field soils. In this study, the chlamydospores of Trichoderma asperellum SM-12F1 capable of As resistance, accumulation, and volatilization were inoculated into As-contaminated Chenzhou（CZ） and Shimen（SM） soils, and subsequently As volatilization and availability were assessed. The results indicated that T. asperellum SM-12F1 could reproduce well in As-contaminated soils. After cultivated for 42 days, the colony forming units（cfu） of T. asperellum SM-12F1 in CZ and SM soils reached 10^10–10^11 cfu g^–1 fresh soil when inoculated at a rate of 5.0%. Inoculation with chlamydospores of T. asperellum SM-12F1 could significantly accelerate As volatilization from soils. The contents of volatilized As from CZ and SM soils after being inoculated with chlamydospores at a rate of 5.0% for 42 days were 2.0 and 0.6 μg kg^–1, respectively, which were about 27.5 and 2.5 times higher than their corresponding controls of no inoculation（CZ, 0.1 μg kg^–1; SM, 0.3 μg kg^–1）. Furthermore, the available As content in SM soils was decreased by 23.7%, and that in CZ soils increased by 3.3% compared with their corresponding controls. Further studies showed that soil p H values significantly decreased as a function of cultivation time or the inoculation level of chlamydospores. The p H values in CZ and SM soils after being inoculated with 5.0% of chlamydospores for 42 days were 6.04 and 6.02, respectively, which were lowered by 0.34 and 1.21 compared with their corresponding controls（CZ, 6.38; SM, 7.23）. The changes in soil p H and As-binding fractions after inoculation might be responsible for the changes in As availability. These observations could shed light on the future remediation of As-contaminated soils using fungi.

Volatilization behaviors of molybdenum and sulfur in vacuum decomposition of molybdenite concentrate

Thermodynamic calculation, ab initio molecular dynamics(AIMD) and vacuum decomposition experiments were performed to study the volatilization behaviors of Mo and S from molybdenite concentrate by vacuum decomposition. In thermodynamic calculation, starting decomposition temperatures of reactions were calculated, and saturated vapor pressures of Mo, S and Mo S2 were also analyzed. In AIMD, geometries of the Sn(n≤8), Mom(m≤8) and MomSn(m+n≤8) clusters have been optimized using density functional theory(DFT) with generalized gradient approximation(GGA). And these clusters were simulated in DFT with Cambridge Sequential Total Energy Package(CASTEP) code of Material Studio software. Structures and stabilities of these clusters before and after molecular dynamics simulations were discussed, and diffusion coefficients were also calculated. In vacuum decomposition experiments, relationship between heat preservation time and volatilization rate of Mo and S was obtained, while the constant temperature and chamber pressure were 1823 K and 5–35 Pa, respectively. Above all, both the theoretical and experimental results showed that volatilization behaviors of Mo and S during vacuum decomposition process of molybdenite concentrate were as follows: Mo could partly evaporate into the condensate in the form of clusters, and S could easily evaporate into the condensate.

Resolving impact volatilization and condensation from target rock mixing and hydrothermal overprinting within the Chicxulub impact structure

This work presents isotopic data for the non-traditional isotope systems Fe,Cu,and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events,as well as those affecting impact structures during the post-impact phase.The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring.Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure.The datasets of bulk Fe,Cu,and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes.The observed Fe and Cu isotopic signatures,with δ^(56/54)Fe ranging from0.95‰to 0.58‰and δ^(65/63)Cu from0.73‰to 0.14‰,mostly reflect felsic,mafic,and carbonate target lithology mixing and secondary sulfide mineral formation,the latter associated to the extensive and long-lived(>105 years)hydrothermal system within Chicxulub structure.On the other hand,the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation.The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast(δ^(66/64)Zn of up to 0.80‰and 0.87‰,respectively)relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn,comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world,as well as for tektites from various strewn fields.In contrast to previous work,our data indicate that an isotopically light Zn reservoir(δ^(66/64)Zn down to0.49‰),of which the existence has previously been suggested based on mass balance considerations,may reside within the upper impact melt rock(UIM)unit.This observation is restricted to a few UIM samples only and cannot be extended to other target or impact melt rock units.Light isotopic signatures of moderately volatile elements in tektites and microtektites have previously been linked to(back-)condensation under distinct kinetic regimes.Although some of the signatures observed may have been partially overprinted during post-impact processes,our bulk data confirm impact volatilization and condensation of Zn,which may be even more pronounced at the microscale,with variable degrees of mixing between isotopically distinct reservoirs,not only at proximal to distal ejecta sites,but also within the lithologies associated with the Chicxulub impact crater.

Effect of the chemical forms of selenium on its volatilization from soils in Chinese low-selenium belt

Bio-availability of different forms of selenium and its rate of volatilization from soils in Chinese low-selenium belt were examined. Adding directly solutions of either inorganic or organic selenium compounds to soil could only slightly increase the rate of selenium volatilization from soil. Volatilization of selenium from soil was largely enhanced when certain nutritional solutions along with selenium compounds were added. Garlic water extract and seleno-amino acids, i.e., seleno-methionine and seleno-cysteine, were found more effective for their bio-availability to the volatilization process. Under laboratory simulating conditions, the volatilization rate of selenium from different types of soils in Chinese low-selenium belt was found in the range of 0.10-0.27 ng.kg-1 soil.day-1 over a 17 days period, generally followed by a decline with time of incubation.

Characteristics of water volatilization and oxides generation by using positive and negative corona

The physical and chemical properties have significant differences for the positive and negative charged particles generated by discharge.In this work,a positive and negative corona discharge system was established,and two discharge reactors for charged particles restraining and acting were designed by a needle electrode covered with a quartz tube and a plate electrode filled with water.The corona discharges happened within the needle-plate electrodes were excited by a positive and negative high voltage source,and the characteristics of both water volatilization and oxides generation were examined within influence of the distances of both quartz tube inside and outside.The results show that the characteristics of both the water volatilization and oxides generation can be affected by the distances of both quartz tube inside and outside.When the distances of tube inside were increased from 5.00 to 13.00 mm,the water volatilizations decreased under negative corona,and increased firstly and declined immediately under positive corona.The maximum value of the water volatilization appeared in the distances of tube inside with 6.00–8.00 mm.In addition,the concentrations of the HNO_(x) and H_(2)O_(2)in treated water decreased with increasing the distances of tube inside.Moreover,with increasing the distances of tube outside from 4.00 to 14.00 mm,the change trends of both the water volatilizations and oxides presented the same as the distances of tube inside,and the maximum value of the water volatilization and oxides appeared in the distance of tube outside with about 9.00 mm.Overall,the positive corona can generate more water volatilizations and oxides in water than negative corona,and non H_(2)O_(2)can be produced by negative corona.The results reflect the difference between positive and negative corona interaction with water,which can provide reference for plasma application.

Model Research on the Effect of Surface Film on Ammonia Volatilization from Rice Field

Pan and field experiments were conducted to investigate the effect of surface film on ammonia volatilization from water and paddy soil. The results showed that the addition of the surface film on floodwater reduced the rate of ammonia volatilization, however, the reduction of the latter varied greatly with its rates of addition. Jayaweera-Mikkelsen ammonia volatilization model with the introduction of a parameter Kf, a relative measure of the resistance of the surface film on ammonia volatilization, was used to elucidate the effectiveness of the surface film on lowering ammonia volatilization. The Kf value was calculated from the results ob-

The Volatilization of Pollutants from Soil and Groundwater: Its Importance in Assessing Risk for Human Health for a Real Contaminated Site

Pollution of different elements (air, water, soil and subsoil) resulting both from accidental events and from ordinary industrial and civil activities causes negative effects on the human health and on the environment. The present paper examines the analysis of a contaminated site, focusing the attention on the negative effects for receptors exposed to soil and groundwater contamination caused by industrial activities. The case study investigated is a contaminated area located in the industrial district of Trento North once occupied by the Italian Carbochimica plant. Pollution in that area is mainly due to contamination of soil and groundwater with polycyclic aromatic hydrocarbons. The methodology applied is the risk evaluation for human health, in terms of individual cancer risk and hazard index. In particular the attention has been focused on a specific migration way: if pollutants in the soil or in the groundwater undergo a phase change, they spread and get to the soil surface, causing a dispersion of vapors in the atmosphere. In this case risk assessment calls for the evaluation of volatilization factor. Among the different models dealing with the estimation of volatilization factor, those mostly known and used in the national and international field of Human Health Risk Assessment were chosen: Jury’s and Farmer’s models. A sensitivity analysis of models was performed, in order to identify the most significant parameters to estimate the volatilization factors among the wide range of input parameters for the application of models. Performing an accurate selection and data processing of the contaminated site, models for the volatilization factors calculation are applied, thus evaluating air concentrations and Human Health Risk. The analysis of the resulting estimates is an excellent aid to draw interesting conclusions and to verify if the soil and groundwater pollutants volatilization affects the human health considerably.

2-22 Study of Oxidation/reduction Volatilization Technology

As an advanced dry head-end processing of spent fuel reprocessing, the oxidation-reduction volatilization technology will use for pulverizing uranium oxide ceramic pellets, decladding, and removal of most of volatile and semi-volatile fission elements, 3H, 14C, Kr, Xe, I, Cs, Ru and Tc, from fuel prior to main treatment process. The AIROX and ORIOX process, including circulation of oxidation in oxygen atmosphere and reduction in hydrogen atmosphere, researched on international at present, is considered to be the first choice for head-end processing.

Evaluation of water management on arsenic methylation and volatilization in arsenic-contaminated soils strengthened by bioaugmentation and biostimulation

Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methylation and volatilization under non-fooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with strawderived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440(GE P. putida). Under fooded conditions, the application of biochar(BC), rice straw(RS)and their combination(BC+RS) increased total As in porewater. However, these effects were greatly attenuated under non-fooded conditions. Compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization,and the promotion percentage under non-fooded conditions were significantly higher than that under fooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation(88 μg/L) and volatilization(415.4 μg/(kg·year)) in the non-fooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOC and p H in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/BC+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-fooded conditions.